This invention relates to a portable readily deployable anchor having a collapsible stock and flukes, and the flukes are releasable if the anchor snags so as to exert a a pull on the anchor's line which pull exceeds a predetermined force. In other words, the release of the anchor is self-tripped by a release mechanism to avoid abandoning a snagged anchor; or, to ensure that small craft such as a canoe, rubber raft, small sailboat or the like is not subjected to a constraint which might damage the boat or cause it to be inundated. This is particularly true of a rubber raft which may be anchored in a swift stream.
Some anchors of this general type have used locking plugs which are to release the snagged flukes when the force on the line exceeds a certain amount, but the greater the pull on the anchor's line, the harder the flukes tend to lock against the locking plugs. To overcome this problem a stockless anchor described in U.S. Pat. No. 4,038,934 was devised, except that to release the snagged anchor, one must first pull on the line with a force greater than a preset force and then slacken the line to unlatch the flukes. It will be evident that slackening the line will not be possible when the craft is anchored in a fast moving stream.
A similar objection and operational disadvantage enures to prior art releasable anchors which require that the line be slackened before it is given a sharp, forceful tug. The requirements for a releasable anchor are particularly acute when it is required to be collapsible so that it can be easily handled and stowed in the limited space available in a small craft. More so than for a small boat, a rubber raft is particularly susceptible to damage from a pointed fluke, not to mention the obvious danger to occupants of the raft. To fill the need for collapsible anchors, numerous such anchors have been described in the prior art, for example in U.S. Pat. Nos. 3,111,106; 3,111,107; 3,485,199; 3,593,682; 3,656,448; 3,747,553; 4,094,264; 4,094,265; 4,098,217; 4,114,554; 4,380,207; 4,385,585; and 4,417,538; inter alia. None of the teachings of the patents suggested that the anchors should be sheathed, nor would there have been any operational relationship of a sheath for such anchors and their flukes, had the anchors been sheathed.
An occasion to sheath an anchor having extendable flukes presented itself in a dynamic anchor described in U.S. Pat. No. 3,187,705 which anchor was designed to descend into deep water with maximum velocity. But the teachings relating to high velocity deep water anchors are inapplicable to an anchor for a small boat or raft which typically operates in shallow water and the velocity of descent of the anchor is of no particular concern.
With particular reference to releasable anchors which are not self-tripped, that is trigger-tripped, the use of a secondary line to trip the flukes by displacing a wedge or locking plug, presents undesirable complications. Whether self-tripped or not, most such anchors have an "open" mechanism, that is, their mechanisms are not protected against silt, grit and debris which tend to lodge in the mechanism and vitiate its reliability.
The importance of providing an appropriate solution to the problem of anchoring small boats was addressed in U.S. Pat. No. 4,004,625 but an appraisal of the scope of this and other pertinent prior art, and an evaluation of the differences between the prior art and my invention indicate that its particular features unexpectedly provide it with the versatility desired in an efficient anchor without sacrificing reliability and ruggedness, and at an economical price.